Actually, making system calls like that is a complete hack. To do a clear screen professionally, you need to utilize the windows API. There are functions that were made specifically for this purpose. You need to basically clear the text buffer of the console application. Look up the console functions at MSDN. Its more complicated that a system call such as system("cls");, but, its a better way to do things.

conio is compiler and system specific, it is not part of the c++ standard lib therefore the compiler manufacturers have different conio headers. Because different systems require different ways of accessing the video, there is no standard way to clear a console app. Clearing the screen is not in any way standard across any platform, therefore there are many ways to do it. For a windows console just use the windows API.